使用rowmapper读取值时出现错误语法SQL异常

Question

这是我的Model类

//Model

    public class CustomerData {

        private String locomotive_id;
        private String customer_name;
        private String road_number;
        private String locomotive_type_code;
        private String in_service_date;
        private String part_number;
        private String emission_tier_type;
        private String airbrake_type_code;
        private String lms_fleet;
        private String aar_road;
        private String locomotive_status_code;

        // Getters and Setters

这是我的RowMapper实现

//RowMapper

    public class CustomerDataResponseMapper implements RowMapper {

    @Override
    public Object mapRow(ResultSet rs, int count) throws SQLException {
        CustomerData customerData = new CustomerData();

        customerData.setLocomotive_id(rs.getString("locomotive_id"));
        customerData.setCustomer_name(rs.getString("customer_name"));
        customerData.setRoad_number(rs.getString("road_number"));
        customerData.setLocomotive_type_code(rs.getString("locomotive_type_code"));
        customerData.setIn_service_date(rs.getString("in_service_date"));
        customerData.setPart_number(rs.getString("part_number"));
        customerData.setEmission_tier_type(rs.getString("emission_tier_type"));
        customerData.setAirbrake_type_code(rs.getString("airbrake_type_code"));
        customerData.setLms_fleet(rs.getString("lms_fleet"));
        customerData.setAar_road(rs.getString("aar_road"));
        customerData.setLocomotive_status_code(rs.getString("locomotive_status_code"));

        return customerData;
    }

}

最后,我在这里得到了我的DaoImpl课程

//DaoImpl
    public String getCustomersData(String locoId, String custName, String roadNumber) {
        CustomerData resultSet = null;
        String str = "";
        if (locoId != null && locoId.length() > 0 && !(locoId.equals("0"))) {
            str = "select   locomotive_id,customer_name,road_number,model_type as locomotive_type_code,to_char(in_service_date,'yyyy-mm-dd') as in_service_date,loco_part_number as part_number,    emission_tier_type as emission_tier_type, "
                    + "air_brake_type as airbrake_type_code,lms_fleet,aar_road,locomotive_status_code   from get_rdf_explorer.get_rdf_locomotive_detail  where locomotive_id = ?";
            resultSet = (CustomerData) jdbcTemplate.queryForObject(str, new CustomerDataResponseMapper(), locoId);
        } else if ((custName != null && custName.length() > 0)
                && (roadNumber != null && roadNumber.length() > 0 && roadNumber != "0")) {
            str = "select   locomotive_id,customer_name,road_number,model_type as locomotive_type_code,to_char(in_service_date,'yyyy-mm-dd') as in_service_date,loco_part_number as part_number,    emission_tier_type as emission_tier_type, "
                    + "air_brake_type as airbrake_type_code,lms_fleet,aar_road,locomotive_status_code   from get_rdf_explorer.get_rdf_locomotive_detail  where customer_name = ? and road_number= ?";
            resultSet = (CustomerData) jdbcTemplate.queryForObject(str, new CustomerDataResponseMapper(), custName, roadNumber);
        } else {
            str = "select distinct customer_name from get_rdf_explorer.get_rdf_locomotive_detail order by customer_name asc";
            resultSet = (CustomerData) jdbcTemplate.queryForObject(str, new CustomerDataResponseMapper());
        }
        return resultSet.toString();
    }

如何根据resultSet中是否存在特定列来有条件地从resultSet获取值.因为我没有通过我的查询得到所有列.

当resultSet中不存在特定列时,我收到SQL错误语法异常.例如,当获取执行不同客户名称的第三个查询时,在resultSet中只有customerName,而不是其他列.

这真的是一个很大的帮助.非常感谢提前.

Answer 1

由于您已经有3个单独的查询,为什么没有3个单独的RowMappers,每个查询一个.您的查询"知道"它们返回的列,因此您可以轻松地为其创建这些类RowMapper.

如果您真的想要High-Fidelity解决方案,您可以RowMapper为公共部分创建抽象基础,为查询的部件指定3个子类.

Answer 2

如果列数不固定，那么您应该ColumnMapRowMapper根据其实现进行选择，即使您不需要创建单独的具体类RowMapper（即CustomerDataResponseMapper），您只需要传递ColumnMapRowMapper查询中的实例，如下所示：

ColumnMapRowMapper rowMapper = new ColumnMapRowMapper();
List<Map<String, Object>> customerDataList =  jdbcTemplate.query(sql,rowMapper, args);

现在您应该创建一种方法来操纵这张地图，例如

    private CustomerData fillCustomerDataFromMap(List<Map<String, Object>> customerDataList){
            CustomerData customerData = new CustomerData();

            for(Map<String, Object> map: customerDataList ){

               customerData.setColumn(map.get("columnName"));
               customerData.setColumn(map.get("columnName"));
               customerData.setColumn(map.get("columnName"));
               customerData.setColumn(map.get("columnName"));

.........
.........
.........
           }
        return customerData;
    }

null这更具可读性，并且删除了样板代码，并且如果映射中不存在列名称，则不会抛出任何异常（如果映射中不存在列名称，它将简单地返回）

参考资料ColumnMapRowMapper：

https://github.com/spring-projects/spring-framework/blob/master/spring-jdbc/src/main/java/org/springframework/jdbc/core/ColumnMapRowMapper.java